AD-AG8G 735 TEXAS UNIV AT EL PASO SCHELLENGER RESEARCH LABS F/ 4/1IBERDIEN CONDENSER INSTRUMENTATION FOR MEASURING HIGH-LATITUDE M--ETC(U)MAY 79 K DOMAGALSKAI J D MITCHELL DAADO7-78-C-0010

UNCLASSIFIED SR2-80-UA-76 NL

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MICROCOPY RI SOION If SI CARI

S.NGER RESEARCHLABORATORIES

E P ELECTRICAL ENGINEERING DEPARTMENT

GERDIEN CONDENSER INSTRUMENTATION FOR MEASURINGHIGH-LATITUDE MIDDLE ATMOSPHERE ELECTRICAL PARAMETERS

II 'gel

I ENGINEERING AND SCIENCE COMPLEX SEP 0 3 1980

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1 qERDIEN CONDENSER INSTRUMENTATION FOR MEASURINGHICH-LATITUDE MIDDLE ATMOSPHERE

, ELECTRICAL PARAMETERS,

SPECIAL REPOT 5/31/79 SR2 -80UA-76

I*Prepared For:

United States Army Electronics Command

Atmospheric Sciences Laboratory

White Sands Missile Range

- New Mexico OTICiiP ELECTE

Submitted By:

.. Electrical Engineering Department

The University of Texas at El Paso

1l Paso. Texas

Klaus Domagaski John D.. /'iot-chell

'~Gaute Research Asgias-nt rs 'X-i6-{ate TF--ofessor

L L TS T STA9TE M N A

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.mSECURITY CLASSIFICATION O F THIS PAGE P A G D 0 E nt - 0 RE D INST RCIO S

REPORT DOCUMENTATION PAGE BEFORE COMPLETING FORM

1. RPORT NUMBER at GV ACCESSION NO3. RECIPIENT'S CATALOG H4UMBER

SR2-80-UA-7V 67 a _,1!1 T (e* Special Report"Gerdien Condenser Instrumentation for May 1979Measuring High-Latitude Middle Atmosphere 6. PERFORMINGORG. REPoT NUMBER

Electrical Parameters"

1. AUTHOR(') S. CONTRACT OR GRANT NUMBER(*)

Klaus Domagalski and John D. Mitchell DAAD07-78-C-0010

9 . PERFORMING ORGANIZATION NAME AND ADDRESS / 10. PRIORM ELEMET. ROJECoitAT. TS

'Schellenger Research/Electrical Engr. DeptThe University of Texas at El PasoEl Paso. Texas 79968

11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATEMay 1979

19. NUNER OF PAGES] 6814. MONITORING AGE1CY NAME & ADORESS('IfWf E*u0e C""eWlhma 0116.) 15. SECURITY CLASS. (01 We* -We, )

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Contract Monitor: Mr. Robert RubioAtmospheric Science LaboratoryWhite Sands Missile RangeNew Mexico 88002

M rV som (Canimm am mvm aft it iseefewr d idUE' Iby N* in6ij

I Middle atmosphere, ionization, Gerdien condenser, electricalconductivity, rocket instrumentationI ,

JI A11 'RACY (C Nm O he N ini"n A" ' *8"*

gGerdien condensers for measuring electrical conductivity,ion mobility and charge number density were flown in recent rocketprograms to investigate the high-latitude middle atmosphere.The instruments were launched in two coordinated programs

j (Aurorozone I and II) at Poker Flat, Alaska to study the effectsof auroral energetics on electrical parameters and in a solareclipse rocket program at Red Lake, Canada. The design of the -I .O. ... .

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L72.

SECURITY CLASUSFICATION OF THIS PAOgWISU, Data J10#6904

Gerdien condenser instrumentation for the Aurarozone IIprogram and the solar eclipse program is considered. Inaddition, electrical parameters measured for the two auroralprograms are presented and discussed. The initi 'al resultsfrom the measurements indicate that high-latitude middleatmosphere electrical parameters are strongly influencedby the auroral energetics.

NTSGP&

S3CDIC TABII~gN Ptg ASWh a.mt4

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ABSTRACT

Gerdien condensers for measuring electrical conductivity,

ion mobility and charge number density were flown in recent

rocket programs to investigate the high-latitude middle

atmosphere. The instruments were launched in two co-

ordinated programs (Aurorozone I and II) at Poker Flat,

Alaska to study the effects of auroral energetics on

electrical parameters and in a solar eclipse rocket program

at Red Lake, Canada. The design of the Gerdien condenser

instrumentation for the Aurorozone II program and the solar

eclipse program is considered. In addition, electrical

parameters measured for the two auroral programs are presented

and discussed. The initial results from the measurements

indicate that high-latitude middle atmosphere electrical

parameters are strongly influenced by the auroral energetics.

vIv i

TABLE OF CONTENTS

Page

Acknowledgements ..................................... iii

Abstract ............................................. v

Table of Contents .................................... viii

List of Tables ....................................... ix

List of Figures ......................................

I. Introduction ..................................... 1

1.1 Middle Atmosphere Ionization Sources ....... 1

1.2 Aurorozone Rocket Program ...................... 2

1.3 Thesis Research ............................ 6

II. Gerdien Condenser Operation ..................... 7

2.1 Theory of Charged Particle Collection ...... 7

2.2 The Gerdien Condenser Launch .................. 13

III. Instrumentation D.esign....; ............. ......... 15

3.1 XRG Paylohd Configuration .................. 15j "

3.2 Gerdien Condenser Design for the XRG 17Payload ....................................

3.3 Solar Eclipse Payload Configuration ........ 22

3.4 Gerdien Condenser Design for the 24Solar Eclipse Payload ......................

3.5 Gerdien Condenser Mechanical Design ........ 28

IV. High-Latitude Middle Atmosphere 32Electrical Parameters ...........................

4.1 Aurorozone I Rocket Program ................... 32

4.2 Aurorozone II Rocket Program ...............

vi

TABLE OF CONTENTS (cont'd)

Page

V. Discussion ...................................... 52

5.1 Aurorozone I Measurements ...................... 52

5.2 Aurorozone II Measurements ................. 61

VI. Conclusion ...................................... 65

6.1 Summary ......... ........................... 65

6.2 Suggestions for Future Research .............. 66

References ........................................... 67

ovi

vii

L1

LIST OF TABLES

Page

Table 1-1 Overview of the launch schedule

(Aurorozone I) ........................... 4

Table 1-2 Overview of the launch schedule

(Aurorozone II) .......................... 5

Table 3-1 Gerdien condenser/blunt probe launch

parameters for the solar eclipse rocketprogram at Red Lake, Canada

(51*N, 94*W) ............................. 23

Table 4-1 Gerdien condenser/blunt probe launchparameters for the Aurorozone I rocketprogram at Poker Flat, Alaska(65-N, 173-W) ............................ 33

Table 4-2 Gerdien condenser/blunt probe launch

parameters for the Aurorozone II rocketprogram at Poker Flat, Alaska(65 0 N, 173*W) ............................ 46

viii

--- 'i ... ?__.._ .?L=__7*___

LIST OF FIGURES

Page

Figure 2-1 Gerdien condenser electrode

configuration ........................... 8

Figure 2-2a Gerdien condenser collection (sweep)voltage waveform ............................ 10

Figure 2-2b Gerdien condenser current responsecharacteristic (example) ................... 10

Figure 3-1 XRG payload configuration .................. 16

Figure 3-2 Gerdien condenser electronic system(Aurorozone II) ......................... 18

Figure 3-3 Sweep voltage circuit (Aurorozone 11)... 19

Figure 3-4 Voltage scalers/level shifters

(Aurorozone II) ......................... 21

Figure 3-5 Gerdien condenser electronic system(Solar eclipse) ......................... 25

Figure 3-6 Sweep voltage circuit (Solar eclipse)... 26

Figure 3-7 Voltage scalers/level shifters(Solar eclipse) ......................... 29

7 iFigure 3-8 Gerdien condenser probe configuration... 30

Figure 4-1 Positive electrical conductivitymeasurements for 0324 AST onSeptember 21, 1976 ...................... 35

Figure 4-2 Positive ion mobility measurementsfor 0324 AST on September 21, 1976 ...... 36

Figure 4-3 Positive ion number densitymeasurements for 0324 AST onSeptember 21, 1976 ...................... 37

Figure 4-4 Positive electrical conductivitymeasurements for 2200 AST onISeptember 22, 1976 ...................... 38

ix

LIST OF FIGURES (cont'd)

Page

Figure 4-5 Positive electrical conductivitymeasurements for 0137 AST onSeptember 23, 1976 ...................... 39

Figure 4-6 Positive electrical conductivitymeasurements for 0220 AST onSeptember 23, 1976 ...................... 40

Figure 4-7 Positive ion mobility measurementsfor 0220 AST on September 23, 1976 ...... 41

Figure 4-8 Positive ion number densitymeasurements for 0220 AST onSeptember 23, 1976 ...................... 42

Figure 4-9 Positive electrical conductivitymeasurements for 2254 AST onSeptember 24, 1976 ...................... 44

Figure 4-10 Positive electrical conductivitymeasurements for 0251 onSeptember 30, 1976 ......................

Figure 4-11 Electrical conductivity measurementsfor 2052 AST on March 21, 1978 .......... 47

Figure 4-12 Electrical conductivity measurementsfor 0026 AST on March 27, 1978 ............ 48

Figure 4-13 Electrical conductivity measurementsfor 0140 AST on March 29, 1978 .......... 49

Figure 4-14 Electrical conductivity measurements

for 0649 AST on March 29, 1978 ............ 50

Figure 4-15 Electrical conductivity measurementsfor 0740 AST on March 29, 1978 .......... 51

Figure 5-1 Piecewise linear fit to the positiveconductivity measurements for 2200AST on September 22, 1976 ............... 54

Figure 5-2 Total energy deposition for 0137 ASTon September 23, 1976 ................... 56

x

LIST OF FIGURES (cont'd)

Page

Figure 5-3 Composite of piecewise linear fitsto the positive conductivitymeasurements for the Aurorozone Iprogram ................................. 57

Figure 5-4 Positive electrical conductivitymeasurements on September 22and 23, 1976 ............................ 59

xi

Lai I'M

CHAPTER I

INTRODUCTION

1.1 Middle Atmosphere Ionization Sources

The middle atmosphere is generally considered to include

the stratosphere, mesosphere and lower thermosphere. In

altitude, this is the region of the atmosphere between

approximately 15 km and 100 km. In situ measurements of

middle atmosphere parameters are largely accomplished using

sounding rockets since most of this region is too high for

balloons and too low for satellites. If the rocket-launched

instrument is deployed on a parachute, the measurement is

typically limited to altitudes below 90 km where the para-

chute becomes wind sensitive and stabilizes.

The ionization sources in this altitude region are of

solar and galactic origin. Under quiescent conditions,

ionization by galactic cosmic rays is the dominant source

for ions in the stratosphere and lower mesosphere [Webber

(1962); Velinov (1968)]. This particular source obviously

shows no diurnal variation, but it is dependent on the

eleven-year solar cycle with the largest cosmic ray intensi-

ties observed during the period of minimum solar activity

[Pomerantz and Duggal (1974)]. Also, the galactic cosmic ray

intensity is dependent on geomagnetic latitude (below 60'),

with the larger values occurring at the higher latitudes.

During the daytime, solar ultraviolet radiation is anI

2

important ionization source in the mesosphere. In particular,

the photoionization of nitric oxide by hydrogen Lyman-ao

radiation (1216 A) is considered the dominant source for

positive ions under quiescent conditions. Other daytime

sources of secondary importance during quiescent conditions

include the photoionization of metastable molecular oxygen0

(02 ('Ag)) by solar EUV radiation (X<1118 A) and the ion-0

ization of all constituents by solar X-rays (X<10 A)

[Aikin (1972)].

At high latitudes, significant enhancements in ionization

are observed during periods of auroral activity. Energetic

electrons are an important ionization source in the mesosphere,

but normally they do not penetrate into the stratosphere.

The interactions between these energetic electrons and

neutral species result in a second source for ions which

is observed in the stratosphere; namely, ionization by

bremsstrahlung X-rays [Freyer (1969); Berger, Seltzer and

Maeda (1974)]. These two ionization sources associated

with auroral energetics are dependent on solar activity

and appear to be rather localized and variable over short

periods of time. Furthermore, ground-based riometers and

magnetometers indicate that these geomagnetic distrubances

occur more frequently at night.

1.2 Aurorozone Rocket Programs

Two coordinated field experiments (Aurorozone I and II)

were recently conducted to study the effects of auroral

3

energetics on the high-latitude middle atmosphere. One

particular objective of these programs was to determine the

effects of these events on middle atmospheric electrical

parameters; particularly, electrical conductivity, ion

mobility and charge number density. Rocket-launched, para-

chute-borne Gerdien condensers for measuring these three

parameters [Pedersen (1964); Rose and Widdel (1972); Conley

(1974); Croskey (1976); Sagar (1976)] and blunt probes for

measuring electrical conductivity [Hale (1967); Hale,

Hoult and Baker (1968)] were flown in both of these programs.

The Aurorozone I rocket program was conducted during

September and October 1976 at Poker Flat Research Range,

Alaska (65*N, 173 0 W). An overview of the launch schedule

for the program is shown in Table 1-1. Two Gerdien con-

densers (G) and four blunt probes (BP) were successfully

flown during this period. In addition, measurements oftemperature (D), ozone (03) and X-ray energy levels (NT)

were obtained as part of this program. A list of supple-

mentary ground-based measurements are also included in

Table 1-1.

The Aurorozone II program occurred during March 1978

and also was conducted at Poker Flat, Alaska. A launch

schedule for this rocket program is shown in Table 1-2.

The Gerdien condenser was flown as part of an integrated

instrument package called the "XRG (X-ray - Gerdien

condenser) payload." In addition to the Gerdien condenser

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measurements, the instrument also measured X-ray energies

and vertical electric field strength. The obvious advantage

of this system is the ability to simultaneously measure

both the X-ray ionization source and the associated electrical

parameters. The flight configuration and size of this

relatively sophisticated instrument were kept small enough

to be launched on a super Arcas rocket and deployed at

apogee on a stabilized parachute (the disc gap band). In

addition to five successful XRG payload flights, additional

measurements of electrical conductivity (BP), temperature

(D), ozone (03) and X-ray energy levels (NT) were obtained

in this program.

1.3 Thesis Research

The development of the Gerdien condenser instrumentation

included with the XRG payload is considered in this thesis.

More recently developed circuitry designed for Gerdien

condensers and a blunt probe flown in the February 1979

solar eclipse rocket is also included. Finally, the Gerdien

condenser and blunt probe measurements from the Aurorozone

rocket programs are presented and discussed.

I

SII

7

CHAPTER II

GERDIEN CONDENSER OPERATION

2.1 Theory of Charged Particle Collection

A Gerdien condenser consists of a pair of concentric

cylindrical electrodes, through which a well-defined axial

flow geometry is developed. By proper biasing of the

cylindrical electrodes and measuring the resulting collected

ion current flowing through the aspirator, it is possible

to determine the electrical conductivity, ion mobility and

charge number density of the air sample. Determining the

ion mobility and charge number density also requires that

the air flow through the aspirator be known. In this section,

the appropriate equations for determining these electrical

parameters are presented. Further treatments of this sub-

ject are considered by Pedersen (1964), Conley (1974), Farrokh

(1975), Croskey (1976) and Sagar (1976).

A schematic of the Gerdien condenser electrode config-

uration is shown in Figure 2-1. The collector has a radius

of ri and a length 1, while the radius of the outer electrode

is r0 A uniform flow velocity <v> is assumed in the axial

direction.

If the outer return electrode is assumed to be at the

potential of the atmosphere, then a negative voltage on the

collector will result in the collection of positive ions and

vice versa. For the Gerdien condensers flown in the Aurorozone

-. r

- ________________ -- 4

0

cr.c

00-J-

9

rocket programs, the collection voltage applied between the

collector and return electrodes has the shape shown in Figure

2-2a and a period of approximately eight seconds. A possible

current response to the voltage waveform as measured by the

collector is shown in Figure 2-2b.

If we start at the origin (V = 0) and consider the

collection voltage being swept negatively, the initial slope

of the corresponding positive ion current response is pro-

portional to the total positive conductivity o+i:

ln(ro/rd dl+(0+1 - 21T 1 dV +< 1 (2-1)

where M

i+ f Z N+M e k+m (2-2)m+mma 1

In this equation, we are assuming that there are M unique

positive ion mobility groups. Actually in the example of

Figure 2-2b, we are considering the case of M=3.

The break in the positive ion current response at t+l

indicates that all of the ions of the highest mobility group

k are collected from the air sample. The collection+1

voltage value V+I at t+l is the minimum value for which a

positive ion of mobility k entering the aspirator at a radial

distance (r - rl) from the collector can still be collected.0 i

The equation for V+1 is

(r o2 r1 2) <v> ln(ro/r dV+= 2 k+1 1 (2-3)

10

V -2

Vs e p V ol a e a ef r

4+1 f.2 t 3

+I-

Figure 2-2b. Gerdien Condenser Currecnt

Response Characteristic (Example)

Thus, solving for the collection voltage at t+1 enables us

to determine the ion mobility value k + 1.

Since at large negative collection voltages all the

ions of mobility k + 1 will be collected from the air sample,

there is no further increase in I+ associated with this

mobility group. The slope between t+l and t + 2 is therefore

relatively smaller in value and is used to determine the

partial conductivity

M0+2 " E N e k (2-4)

+2 2 +mr +-r

This development continues with each additional breakpoint

indicating when the next highest mobility group is completely

collected from the air sample. The general equations to

determine the values of the different ion mobility groups

and their corresponding concentrations are:

2 r2(r i ) <v>ln(r0 /r (

k+m =2 V +ml 125

N4- 0 +m -+(M+l) (2-6), N+ m e k +m(26

In reexamining Figure 2-2, there are several points

worth noting. First, for a sufficiently large negative

collection voltage such that all positive ions are collected

from the air sample, the current response becomes flat for

increasing voltage. This is the saturation mode of operation

and the positive ion saturation current is simply

_ _ _ _ _ P- ME mw,

12

2 r 2) N+ q<v> (2-7)

Under the saturation condition, the positive ion current

value may be used to determine the total positive ion number

density.

Secondly, the development for obtaining the equations

describing the collection of negative charge species is

similar. If free electrons are present as shown in Figure

2-2b, their mobility values are so much greater that there

appears at the origin approximately a step increase in cur-

rent. The I-V response of Figure 2-2b shows the collection

of electrons and two different negative ion mobility groups.

The corresponding equations for determining total negative

conductivity (a_1) and the mobility and density values of

ion mobility group k are respectively:-p

ln(ro/ri) dl

-0 1 2r 1 t1 <t<O (2-8)

where* PE = N e k (2-9)

-P -P

2 2(r° - ri ) <v>ln(ro/r )

-p 2 V 1-p

0 -0O

Np -(p+1) (2-11)-p ek -p

In writing these equations, it is assumed there are P

different mobility groups for the negative charge species.

j __________________ ________________

13

Finally, if relatively immobile ions are present in

an air sample, the actual range of collection voltages for

the Gerdien condenser might not be sufficient to achieve

saturation. If this is the case, then one is unable to

determine the values for these less mobile groups which are

not saturated out nor the total ion density.

2.2 The Gerdien Condenser Launch

The Gerdien condensers in the Aurorozone I and II rocket

programs were flown on super Arcas rockets. Prior to the

launch, the instrument is calibrated by connecting a known-

value resistor (RCAL) in parallel with the Gerdien condenser

electrodes. The electrometer's output response when the col-

lection voltage waveform is applied across the resistor is

received through the telemetry system and recorded on mag-

netic tape.

The actual in-flight measurements are obtained after the

payload separates from the rocket at apogee and is descending

on a stabilizied parachute system. The telemetered in-flight

data are received by a ground-based system and recorded on

magnetic tape.

The probe's position and velocity during the flight

are obtained by using a radar. For the recent Gerdien

condenser flights conducted during the solar eclipse, how-

ever, a transponder was included with the transmitter

system to provide ranging information. The ranging data

along with the azimuth and elevation angles from a GMD-4

14

telemetry receiving system were then used to determine the

probe's position and velocity. This particular transponder

system was used for rocket flights when radar tracking was

not available.

Upon completion of the rocket flight, the data are

played back onto a strip chart for reduction. The actual

equation used for scaling the data is dependent on the

probe's electronics, and is included in Chapter 4.

15

CHAPTER III

INSTRUMENTATION DESIGN

3.1 XRG Payload Configuration

The sensor configuration for the XRG payload is shown

in Figure 3-1. As discussed previously, the XRG payload

combined a Gerdien condenser with an X-ray scintillation

detector and an electric field sensor. When the instrument

package is deployed on a parachute, the Gerdien condenser

is oriented downward. The air flow through the aspirator

is determined from the instrument's descent velocity which

is measured by a ground-based radar. Payload orientation is

determined using a two-axis magnetometer.

In flight, the aperture for the X-ray scintillation

detector is directed upward. The detector uses sodium

iodide (Nal) crystals which floresce when impacted by X-rays.

The resulting photons are detected by a photomultiplier

tube. The X-ray energies are measured in four different

ranges: 5-10 keY; 10-20 keV; 20-40 keV; and greater than

40 keV. In addition, a Geiger-Mueller tube for measuring

energetic electrons and monitoring cosmic rays was included.

The electric field sensor consists of a probe mounted

at the base of the parachute and connected to the payload

body by a two-meter wire which spirals around the parachute

lanyard. The vertical electric field is determined by

measuring the voltage between the probe and the payload

body.

16

XRG PAYLOAD

1-10 cm-§' PARACHUTE ATTACHMENT &

E FIELD ANTENNA

X-RAY DETECTOR W& PREAMPEt GUARD COUNTERS

F=:9 ! H.V. SUPPLIES

BATTERIES & CONVERTERS

PULSE Et COUNTING ELECTRONICS;Z7 ASPECT SENSOR

TM PACKAGE87 cm TRANSMITTER Et ANTENNA

I PROBE ELECTRONICS

I GERDIEN PROBE

ig I\I

, ~ I I

\ /' \I

Figure 3-1, XRG Payload Configuration

Ipi .- . . . . . . .. :_ " ~ -... . . " . .-. ..-. .

17

The transmitter and electronics are housed in a 10.2

cm diameter fiber glass cylinder which has a 1680 MHz micro-

strip-type antenna photoetche on the outside surface. The

PCM encoding system provides a bi-phase level output with

nine words per frame and eight bits per word at a bit rate

of 8k bits/second. The encoder input accepts a 0-5 V analog

voltage waveform. All of the electronics are powered by

six PMI silver cell batteries.

3.2 Gerdien Condenser Design for the XRG Payload

A sketch of the electronics system associated with the

Gerdien condenser is shown in Figure 3-2. The sweep voltage

waveform provides a known collection voltage waveform to the

guard portion of the inner collecting electrode. By connecting

the guard electrode to the electrometer's noninverting input

terminal and the collector to the inverting input terminal,

the collector is also "virtually" at the sweep voltage po-

tential. It was necessary to bias the outside skin of the

XRG payload at ground potential in order to keep the probe's

electronics compatible with the X-ray detector and the elec-

tric field probe.

A circuit diagram for the sweep voltage generator is

shown in Figure 3-3. The waveform shown in Figure 3-3 is

obtained by using an astable multivibrator followed by a

constant current run-down circuit. The sweep voltage ob-

tained at the output of the LM 264 operational amplifier

follower is connected to both the noninverting terminal of

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the electrometer and a voltage difference amplifier.

Regulated voltage values of ± 12 V were supplied to the

sweep voltage circuit using a LM 126H voltage regulator.

The current of charged particles drawn to the collector

is measured by an electrometer (Figure 3-2). The electro-

meter for the XRG payload uses a Burr-Brown 3523L operational

amplifier which has a nominal input bias current of 0.1 pA

and a 100 dB common-mode rejectio ratio. A Victoreen

MOX-400A resistor of value 1 x 109 ohms is used in the

feedback path. For supply voltages of ± 12 V and a common-

mode voltage (the sweep voltage) ranging between ± 8 V,

the electrometer's measurement range is approximately

± (2-3) nA.

After differencing the sweep voltage from the electro-

meter output signal, the data waveform is fed to three

parallel voltage scalers/level shifters (Figure 3-4). The

* " level shifting produces a 0-5 V analog signal compatible

with the PCM encoder. The scaling operation results in

data current ranges of approximately: ± 2 x 1.0 nA

(Channel 1); ± 2 x 0.125 nA (Channel 2) and ± 2 x 0.025 nA

(Channel 3). The multi-channel telemetry capability of the

XRG payload is advantageous in that it enhances the Gerdien

condenser's measurement range to approximately four decades.

The two less sensitive current measurements were allocated

separate telemetry channels while the most sensitive

current channel was assigned to a commutated channel. In

* -

21

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0

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-A-I

it.

22

addition, monitoring of the sweep voltage and the battery

voltage levels was also telemetered on the commutated

channel.

3.3 Solar Eclipse Payload Configuration

The Gerdien condenser designed for the February 1979

solar eclipse rocket program included a magnetometer and

PCM encoder similar to those used with the XRG payload.

The remote launch site necessitated the inclusion of a

Space Data Corporation PWN-10A 403 MHz transponder for

ranging information. The transponder uses an 83 kHz pulse

waveform to modulate the plate voltage of the RCA 4048V3

1680 MHz transmitter. The antenna housing for this payload

was also a 10.2 cm diameter fiber glass cylinder with strip

line antennas for both receiving the upleg 403 MHz signal

and transmitting at 1680 MHz.

The relatively smaller payload length (48.9 cm) and

weight (2.930 kg) afforded a somewhat higher flight

'apogee (nominally 80 km) where the payload separated from

the super Arcas rocket and was deployed on a stabilized

parachute (either a disc gap band or starrute).

At the time of this writing, only the launch dates and

times are known for the Gerdien condensers and blunt probes

flown in the solar eclipse rocket program. These launch

parameters are listed in Table 3-1.

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4 4- 4. (*)

4-41 Cu Cu u. - - ~ 4 -4

od Co cid 4.0 -4 02 '- 4h4 .

Ena 2- U w V). *V) En 0

Ou w

0 00 Cu 0u C C u 4 0u C

E-4 0 *2 - 4' 4' . 0 u. 0 -

0. 0 0 4 . 0 0. 0

E-4 C~

C/3 0)uCI Co Cu 0 o

z 0 e Cu LI) M C) 0uC

. 0 0 0 C14 0 .0C

ON C-4 C4 04 C4 C4 C 04 )

'Pk 4 4 '4 4 *4 4 ;%4 W

24

3.4 Gerdien Condenser Design for the Solar Eclipse Payload

A schematic for the Gerdien condenser electronic

system is shown in Figure 3-5. The sweep voltage waveform

is similar in shape but has approximately twice the range

as that used for the XRG payload. The noticeable difference

in operation is that the return electrode and payload skin

are biased at the sweep voltage and the inner guard electrode

is grounded, thus avoiding the need for a voltage difference

amplifier following the electrometer. The electrometer out-

put is connected directly to three parallel voltage scalers/

level shifters which in turn, are connected to individual

channels of the PCM telemetry system. As previously dis-

cussed, the PCM encoder and transmitter system - ex-

cluding the transponder - are similar to these flown on

the XRG payload.

The sweep voltage circuit is a different design as

shown in Figure 3-6. This particular circuit produces a

periodic voltage waveform with negative-going ramp that

is limited by the two supply voltages, in this case ± 16 V.

For the operational amplifiers (op amps) numbered one

to four, a LM224 quad op amp was used. Op amp number 5 is

a LM 741. The circuitry with op amp 1 forms a square wave

generator which can be monitored at PI. The 2N3821 silicon

n-channel junction field-effect transistor (JFET) and op

amp 3 form a constant current sink for C 2. Op amp 2 is

used as a comparator to give the negative-going voltage

T7

25

U) 0

w cc

4 9- 9-w hCD u 2-

x@

w a. hi>J >

9- hi I- ..$ 0tT -

Ol0

1 PA 26

0-

W CWE 00-

z cc00

00~

4-

a. 0w Uw

0.0

onn

400z>

CL)

* 40 002

00

>. on

zw)c

27

ramp a hard limit at approximately -15 V. The output of

the LM741 op amp follower is connected to the return

electrode and it also drives an op amp inverter (number 4)

and another LM 741 op amp follower (not shown). This

additional op amp follower biases the payload skin at the

sweep voltage and avoids possible r-f noise leaking back to

the initial sweep output. The inverted sweep voltage

waveform is used for displacement current cancellation at

the electrometer input.

The electrometer (Figure 3-5) uses the Burr-Brown

3523L operational amplifier with a Victoreen Hi-Meg feed-

back resistor (Rf) of either 5 x 109 I x 10 or 2 x

1010 ohms. The current measurement range is approximately

(± 15/R f) amperes. This particular current range is allo-

cated to one data channel, with current ranges 8 and 64

times more sensitive inputted to other separate data channels.

The Gerdien condenser displacement current associated

with the sweep voltage is large enough to saturate the most

sensitive current measurement range. Therefore, a scaled

inverted sweep voltage connected to a low leakage capacitor

is also supplied to the electrometer input to cancel the

other displacement current component. The very sensitive

electrometer and the appreciable electrode capacitance

(Z 2 pF) make it necessary to strongly filter any noise

riding on the sweep voltage, thus reducing possible noise

displacement current to the electrometer input.

28

The voltage scalers/level shifters shown in Figure

3-7 set the current range sensitivities and produce voltage

levels (0-5 V) compatible with the PCM encoder.

3.5 Gerdien Condenser Mechanical Design

The mechanical design of the Gerdien condenser for the

XRG and solar eclipse payloads is similar. A drawing of the

electrode configuration is shown in Figure 3-8.

The Gerdien condenser electrodes consist of an inner

collector with a guard electrode and an outer return elec-

trode. The collector and guard are copper, and are sepa-

rated and alligned by a nylon spacer. The collector's out-

side diameter is 1.587 cm and its length is 6.350 cm. A

brass threaded rod connects the collector and provides an

electrical conducting path to the electrometer. The guard

reduces fringing of the electric field at the joined end

of the collector and shields the collector's conducting

rod from r-f pickup and photoemission from the sun. The

collector also needs to be shielded from the sun by the

return electrode to avoid possible photoemission. The outer

return electrode is aluminium and has an inside diameter of

7.46 cm and a wall thickness of 0.079 cm. The free space

capacitance of this concentric electrode configuration is

approximately 2 pF.

The delrin piece to which the return electrode is

connected is flared to improve the air flow geometry through

the aspirator. The electrometer is housed within the

, . . ... ... , ...- .... - . . . .- i . .

29

N 0 .K *U K N' U U

+ + 0)

.)

0. a< u(0 Ez

0

to > N> >

"CO

+ +

[, -

* 4. 1* o

30

OUTER ELECTRODE

II _ROD

III IINNER ELECTRODE

COLLECTORII

NYLON SPACER

IIGUARD

SI NOt I t

S IjI, I _

IlItI II

: I I ( ELECTROMETER -1:

|!I II IL----OUSIN G).. Ji

Figure 3-8. Gerdien Condenser Probe Configuration

IIIIIIIII

31

delrin piece, with the electrometer circuitry contained

inside an aluminum cup. The aluminum cup shields the

electrometer circuitry from possible noise, and electrical

connections to the circuitry are made with Erie-003 rfi

filters.

The flared delrin piece fits to the fiber glass antenna

housing described earlier. Three bolts in the axial direction

align the printed circuit boards inside the antenna housing

and keep the entire instrument package together.

7 _

32

CHAPTER IV

HIGH-LATITUDE MIDDLE ATMOSPHERE ELECTRICAL PARAMETERS

Middle atmosphere electrical parameters measured in the

Aurorozone I and II programs are presented in this chapter.

The equation for reducing the Gerdien condenser electrical

conductivity data, which is dependent on the electronics

and the preflight calibration, is also presented.

4.1 Aurorozone I Rocket Program

A list of the launch parameters for the Aurorozone I

rocket instruments measuring electrical conductivity is

presented in Table 4-1. Although the emphasis of this

research is concerned with the Gerdien condenser flights,

electrical conductivity data from the parachute-borne blunt

probes are included since these measurements are relevant

to future discussion.

The electrode biasing scheme for the Aurorozone I

Gerdien condensers (and also for the recent solar eclipse

payloads -see Figure 3-5) involved biasing the outer return

electrode and payload skin at the sweep voltage with refer-

ence to the inner guard electrode (and virtually the collector).

Applying Equation 2-1 and 2-8 to this probe electronics

scheme, the equation for determining the positive and nega-

tive electrical conductivity values is

In(ro/ri) (dV+/dt)DATA (4-1)

- 2 lIRCAL (dV/dt) CAL

".Ir. . ."

33

C.,Y

*.-P4 V4~4-J~ ~ 0)O Q

~ d I' I4 . 4 k J

00 oJ~~J

0E-4~ r .-

0) 00 In 0UN 0 0

w00

pq - 1 0 0 0 0

044 14 q

0 04: )0

'4: Cl c C

N C4 04 .4 (N 0 .

P ~ 4 w 0w 0 0

34

In this equation, ro, ri and I are Gerdien condenser probe

dimensions as defined in Chapter 3. The calibration resistor

value is R CAL . Finally, the expressions (dV±/dt)DATA and

(dV/dt)CA L are the time rates of change of the electrometer

output voltage in flight and during preflight calibration,

respectively. The procedure for obtaining these waveforms

is discussed in Section 2.2.

The electrical conductivity data for the Gerdien con-

denser flown at 0324 AST on September 21, 1976 are plotted

in Figure 4-1. The corresponding positive ion mobility and

charge number density values for this flignt, which were

scaled using Equations 2-5 and 2-6, are plotted in Figures

4-2 and 4-3, respectively.

Electrical conductivity values for the blunt probes

flown on September 22, 1976 at 2200 AST and September 23,

1976 at 0137 AST are shown in Figures 4-4 and 4-5, respec-

tively.

The second Gerdien condenser flown in this program was

launched on September 23, 1976 at 0220 AST. The positive

conductivity, ion mobility and charge number denisty data

for this rocket flight are plotted in Figures 4-6, 4-7, and

4-8, respectively.

Finally, the last two rocket payloads for measuring

electrical conductivity in the Aurorozone I program were

blunt probes launched on September 24, 1976 at 2254 AST and

September 30, 1976 at 0251 AST. The electrical conductivity

35

0

IL-44

'00 0

0 11=4%

IV

I 0jLU'H '=

* 4

-IC*

t9 m Ito ~

k ~.to

36

I-.00'

0

CL A.- J ijj N 0LL (n K) + 1

C14

0 0

4

Ugj

o0P.4

00

00 0

37

y 0

+

0~

-W C\J

aa

ow %

00

0 0 v-I

.nr-

38

0

10 04

0-. 44

aima%J

0 N

> 0

lj- 4 ZU ge

4 '4 04 CON

19 U

404

w

.4J

00 a)

41'1

4

39

0

0 1~*H

0U 0

0m

ON-h

40

0

0V4.

UV)

#44 0

L9-4

0

94

'14 9-4

4 C4t9 0-40V4 0

.4>4

P--A I

t9O

4*L

41

(D 0

o- +

00 oD00LL- (J CI A .

00w o + 44

Y.-..- . U, .

0 0 U

0i0

0

-

*4 a)%% ~~a) ).

.- 94

42

CL 0 T

LLv)C\ A C'4

0Qo+

00

* a

a 0 00 000 a

0

0 C4

, 4 -

JI)

.o4

LOQ

43

data from these two rocket flights are shown in Figures 4-9

and 4-10 respectively.

4.2 Aurorozone II Rocket Program

Five Gerdien condensers--part of the XRG payloads--

and two blunt probes measured middle atmosphere electrical

parameters in the Aurorozone II program. Launch parameters

for these rocket flights are listed in Table 4-2. For the

XRG payloads, the outer return electrode and payload skin

were grounded and the inner guard electrode and collector

were biased at the sweep voltage (see Figure 3-2). With

this probe biasing configuration, it can be shown that

Equation (4-1) is still valid for reducing the electrical

conductivity values.

The Gerdien condenser electrical conductivity data for

the five XRG payload flights are presented chronologically

in Figures 4-11 to 4-15.

I

ii44

44

0

CN(N

00

CL 41V Q)4-'l

LL4)U

L 0

44-

1'a 4 >

>4 0'

r4 '1

jz4

45

'-4

+44- 0

N >

Lfl)c C) 0

-4,4 M

04 0)

'-4

:j

46

Q) 0 0 Q

41I 41 41 &jl 4w .

( 00 J 4.1 41- 4.1 4.1 0

0 0 CrC 9 mc

00

w0 w4 w0 00 w4 (4 0

4-1 4 04 -cc 14 04 -CC < 0

27 $ 4 14 14 w4 w4 4 w4 1o 0 0 a) 0 0) ) ) 0 a) 0)

'04

L) 0 0 0 L) u 0

U)U U 2 )C

H 4.10) 0 0 4p 4 ~.

U ~ ~ 0 ~ ~ ~ ~ 0) 0

Ci) C 0 0 0

o 14 CI C14 It It -4 -Tim u 0 -I 0 en %D 0 0

z 0 1 140C0- C.4L) 0

HH

0 rs~ 4 C4 C4 C14 -C4~

w U4 1 4 04 .4 $4 14 $4 04-W 0 04C4 0 0 0 0 0 c-a

47

-4

U) U1Ctu

... 1..

wic '-4 : 0 W

~~En

0

LL o"C1

• -I -IU

L "4

0 A

.4

(6N, 3an.-iv-

48

co

'-44

0

,-#-4

014L E 0

'-4

44 1

4* -4

-4Z

49

Go

00

'E-4

Nt)9

LLO -W00

441'

O0)v4

4rf4

'-44

44$4

#1 -?"

50

0ofa%

-4

0

-41

<W)- 0

I CA

LL F o (0

L (04I0.Liu Of) ",.1

0) (D3

'S '- 0

G I 0

.II

"*. . Li

'_ _ _ _ _ _ '_I_ _I__ _I_ I I o

tgg

(WU> 30.9ifi17f-4

51

[.,3

co

tn 1.4-4

'-4

.Jv4Li +

I"

4 ,4.

LL(JU) 1.4

L (0

ta m

'.-4

i-

4

52

CHAPTER V

DISCUSSION

The middle atmosphere electrical parameters measured

by Gerdien condensers and blunt probes in the Aurorozone

I and II rocket programs are discussed in this chapter. Geo-

magnetic conditions as determined from ground-based magne-

tometers and riometers at College Station and Fort Yukon4

Alaska are qualitatively described for the launches in

Tables 4-1 and 4-2. Although several flights in these tables

are classified as occurring during geomagnetically quiet

periods, probably the quietest period was the evening of

March 21, 1978.

5.1 Aurorozone I Measurements

The Gerdien condenser and blunt probe rocket launches

for the Aurorozone I program were all conducted at night,

since this period is usually more geomagnetically active.

It also should be a somewhat simpler period for studying

auroral ionization effects since there is no influence at

higher altitudes from solar ionization sources.

Under geomagnetically quiet conditions, the dominant

ionization source in the stratosphere and lower mesophere is

associated with galactic cosmic rays, and it essentially

displays an altitude dependence proportional to that for

neutral number density. The corresponding altitude depen-

dence for electical conductivity in the galactic cosmic

LA

53

ray ionization region is nicely demonstrated by the low

altitude electrical conductivity data for the Aurorozone I

program. As an example, the positive ion conductivity data

for 2200 AST on September 22, 1976 are plotted in Figure

5-1, with a piecewise linear fit constructed to the data

points. (Only positive ion conductivity data are shown for

the Aurorozone I program. The negative conductivity mea-

surements are generally comparable in value to the positive

conductivity data.) The straight line fit at the lower

altitudes is indicative of the altitude dependence of elec-

trical conductivity in the galactic cosmic ray ionization

region.

Above 50 km, the electrical conductivity values break

to the right, indicating a conductivity enhancement above

the associated galactic cosmic ray background level (shown

by the dashed line). Interestingly, it is also possible

to construct a straight line fit to these high altitude

data. The enhancement in conductivity is thought to result

from aurorally-induced bremsstrahlung X-ray ionization.

The breakpoint for the piecewise linear fit to the data

thus shows how low the bremsstrahlung X-ray ionization

penetrates into the atmosphere.

The presence of this additional ionization source at

higher altitudes is substantiated by the X-ray data obtained

from the two Nike-Tomahawk flights (September 21 and 23, 1976).

Energy deposition deduced from the X-ray energy data for

ad . .

- -- ~ -=77

54

00

'.40

IL-

Lm 0) r

> O

#4 Q)u

0 0

' Z4 0 01

0 C,

I Co W

0

'.4 z$4J

.4r

EmuE

55

September 23 are shown in Figure 5-2 [Goldberg and

Hilsenrath (1978)]. Examining this figure, we see that the

energy deposited below approximately 40 km is primarily

from galactic cosmic rays. In the 40 to 55 km altitude

region, ionization is largely associated with 5 keV

bremsstrahlung X-rays. At higher altitudes, 100 keV ener-

getic particles become an important ionization source.

The general altitude structure for the September 22,

1976 conductivity data is actually observed to some extent

in all of the Aurorozone I measurements. A composite of the

piecewise linear fits constructed for five sets of positive

conductivity data from the Aururuzune I program is shown

in Figure 5-3. The legend in the figure identifies the

different curves and also indicates the corresponding

altitudes of the ionization breakpoints.

For the night of September 22 to 23, 1976 which was

the most active of the measurement period, the bremsstrahlung

X-ray ionization effects are observed as low as 45 km

(following an auroral event). In fact, the three sets of

data obtained during that night show the X-ray ionization

effects penetrating continually lower as the event progresses.

The data for September 21, 1976 were also obtained during

a period of geomagnetic activity. The activity for this

period was not as strong, as might be inferred from the

relatively higher ionization breakpoint (approximately 51 km).

The electrical conductivity data for 0251 AST on

. Lg 7

56

.000

-UQ)-z

LU)UJJ

w 44

/n 0CD c~

0>00 0

CQ) L)

LU)

Goo

(W M- 3a.LiJ

57

-o

C-i W

4-

CL -

Cj)~~C~ C/ -C)H

0

n~- NV -

E cv

0 .. cL . -L o- a.-r

U) U)U Cl) UI- )I-

0- OOcl n oOto -Y N- N~ C.

0i 0000000)wC

(W4) z

58

September 30, 1976 were obtained during the quietest measure-

ment period of the Aurorozone I program. Based on the

conductivity enhancements observed above 54 km, it would

appear that this period was not actually that quiet. In

fact, there were probably ionization effects due to auroral

energetics present to some extent throughout the entire

measurement period.

Conductivity measurements for the three-launch sequence

on the night of September 22 to 23, 1976 are shown in Figure

5-4. With the data for 2200 AST used as the reference,

we see conductivity enhancements in the high altitude data

for 0137 AST which was the most active period during the

auroral event. The positive conductivity data obtained at

0220 AST following the event, however, show a recovery from

the conductivity build-up at higher altitudes. Interestingly,

at the lower altitudes where it appears the bremsstrahlung

X-rays do not penetrate, an overall increase in ion conduc-

tivity is observed.

As developed earlier, the Gerdien condenser measures

ion mobility and charge number density as well as electrical

conductivity. The ion mobility and charge number density

values for 0220 AST on September 23, 1976 are shown in

Figure 4-7 and 4-8, respectively. As many as three distinct

positive ion mobility groups were measured at some of the

higher altitudes. In general, it appeared that ion satu-

ration was not achieved which would imply that at least one

1J

59

U),U

0 r- (0

*k 0 0..a

LU 0) Cl) Ml

uCu

'-4

+ 0 N r4) J

$4

cc )

'41

0)

04

Lin

p p p

60

additional mobility group with values to the left of the

dashed line was also present in the air sample. The

straight line in Figure 4-7 is drawn to fit the highest

mobility group, which is present over the entire altitude

region.

The positive ion concentrations corresponding to the

different ion mobility groups in Figure 4-7 are shown in

Figure 4-8. The highest ion mobility group has a concen-03 -3

tration of approximately 1 cm over the entire altitude

region, with the less mobile ions having generally smaller

number densities.

If the ion mobility values (Figure 4-7) for the highest

mobility group and the corresponding number density values

(Figure 4-8) are used to compute electrical conductivity,

it is observed that this particular mobility group accounts

for the electrical conductivity component associated with

galactic cosmic ray ionization. The less mobile groups,

which are observed at the higher altitudes where there is

ionization by bremsstrahlung X-rays, appear to account for

the enhancement in conductivity above the galactic cosmic

ray ionization level. Possibly, the less mobile ion species

result directly from this additional ionization source,

but more likely, the bremsstrahlung X-rays influence the

chemical processes in the region leading to the formation

of less mobile species.

Similar results are observed for the Gerdien condenser

61

ion mobility (Figure 4-2) and charge number density (Figure

4-3) data for 0324 AST on September 21, 1976. It should be

noted that both Gerdien condenser rocket flights for the

Aurorozone I rocket program occurred during geomagnetically

disturbed conditions and thus no ion mobility and charge

number density data were obtained for quiet conditions.

As mentioned earlier, even the electrical conductivity

data obtained during periods which appeared from ground-

based measurements to be geomagnetically quiet were, in

fact, also affected by auroral energetics.

5.2 Aurorozone II Measurements

The XRG payloads flown in the Aurorozone II program

were heavier than the Gerdien condensers in the Aurorozone

I program, and thus measurements above 60 km are limited.

Futhermore, the Gerdien condenser launch schedule for the

Aurorozone II program is more diversified, including night-

time launches under both geomagnetically quiet (2052 AST

on March 21, 1978) and disturbed (0026 AST on March 27 and

0140 AST on March 29, 1978) conditions and launches during

morning twilight under geomagnetically disturbed conditions

(0649 AST and 0740 AST on March 29, 1978). The dots in

Figures 4-11 to 4-15 represent measurements for which the

positive and negative conductivity values are equal. The

plus and minus signs include instances when there were

small differences in the respective positive and negative

conductivity measurements. In general, we see that the

aw -- --

62

differences in the polar conductivity values at these alti-

tudes are relatively small.

The electrical conductivity measurements for March 21,

1978 (Figure 4-11) are in general agreement with what is

expected for geomagnetically quiet conditions. The altitude

dependence for electrical conductivity throughout the entire

measurement region would indicate that galactic cosmic ray

ionization is the dominant source for ions, and no noticed

ionization enhancements associated with auroral energetics

appear significant at the higher altitudes. A wave-like

effect on the conductivity data is observed at the higher

altitudes which possibly reflects the dependence of ion

mobility on pressure. Considerable payload swing was

observed during the flight making further reduction of the

data to determine ion mobility and charge number density a

difficult task.

The two nighttime conductivity measurements obtained

under geomagnetically disturbed conditions in the Aurorozone

II program demonstrate general trends consistent with the

data for the Aurorozone I program. If the electrical con-

ductivity measurements for March 21, 1978 (Figure 4-11)

are used as a reference, the data for March 27, 1978

(Figure 4-12) show enhancements in electrical conductivity

at all altitudes above 37 km. The nighttime electrical

conductivity measurements for March 29, 1978 (Figure 4-13)

I=WWW

.4

63

are relatively larger than the reference values for March

21, 1978 at all altitudes.

Probably the most interesting result is observed in

comparing the three sets of nighttime data at the lower

altitudes. While there is generally good agreement between

the data sets for March 21 and 27, 1978, which is to be

expected if the ionization is principally controlled by

galactic cosmic rays, the nighttime measurements for March

29, 1978 show a marked enhancement in conductivity. Thus,

it would appear that the auroral energetics do, on occasion,

influence ionization processes even in the lower stratosphere.

The morning twilight data for 0649 AST and 0740 AST

on March 29, 1978 (Figures 4-14 and 4-15, respectively)

were obtained during a geomagnetically disturbed period.

The battery life was relatively short for the payload flown

at 0740 AST, and thus electrical conductivity data were

obtained only down to 43 km, If the electrical conductivity

measurements for either of these flights are compared to

the reference data of March 21, 1978 obtained under geo-

magnetically quiet conditions, there are observed conductivity

enhancements at higher altitudes which are again thought to

be associated with auroral energetics.

In comparing the two morning twilight conductivity

measurements, it is observed that the conductivity values

for 0740 AST are relatively larger than these for 0649 AST.

1.

64

This early morning enhancement in conductivity at these

altitudes is thought to be at :east partly attributed to

a photodissociation process resulting in the formation of

more mobile ion species [Mitchell, Sagar and Olsen (1977)].

I - ,

*I

65

CHAPTER VI

CONCLUSIONS

6.1 Summary

The initial results from high-latitude ionization

studies of the middle atmosphere indicate that auroral

energetics strongly influence electrical parameters in this

altitude region. Nighttime measurements of electrical

conductivity from two field programs at Poker Flat,

Alaska - Aurorozone I and II - showed enhancements in

electrical conductivity during periods of auroral activity.

These conductivity enhancements in the stratosphere are

thought to result from ionization by bremmstrahlung X-rays

emitted at higher altitudes. The region in which the

conductivity enhancements were observed corresponds to the

altitudes in which X-rays were measured by other experiments

flown in these programs.

The Gerdien condensers were also used to measure ion

mobility and charge number density in addition to electrical

conductivity. The ion mobility data from the two Gerdien

condenser flights in the Aurorozone I program indicate the

presence of additional lower-valued ion mobility groups in

the region where the bremmstrahlung X-ray ionization is

observed. Furthermore, the conductivity values computed

using these particular mobility groups and their corresponding

density values account for the bremmstrahlung X-ray-associated

66

conductivity enhancements. Thus, it appears that the ion

chemistry is modified by the auroral energetics, resulting

in the formation of new and different ion species.

6.2 Suggestions for Future Research

Further studies are needed to better understand how

middle atmosphere electrical parameters and other neutral

parameters are affected by auroral energetics. Such programs

preferrably should include integrated instrument packages

such as the XRG payload which is capable of measuring both

the source parameters and the affected electrical parameters.

Finally, a complete understanding of auroral related energetics

and their influence on ion chemistry also requires that

measurements be made during geomagnetically quiet conditions.

67

REFERENCES

1. Aikin, A.C., Ionization sources of the ionosphericD and E regions, Aeronomy Report No. 48, 96, 1972.

2. Berger, M.J., S.M. Seltzer and K. Maeda, Some newresults on electron transport in the atmosphere,J. Atmos. Terr. Phys. 36, 591, 1974.

3. Conley, T.D., Mesospheric positive ion concentrationmobility and loss rates obtained from rocket-borneGerdien condenser measurements, Radio Sci. 9,575, 1974.

4. Croskey, C., In situ measurements of the mesosphereand stratosphere, Scientific Report No. 442,Ionosphere Research Laboratory, Pennsylvania StateUniversity (1976).

5. Farrokh, H., Design of a simple Gerdien condenser forionospheric D-region charged particle density andmobility measurements, Scientific Report No. 433,Ionosphere Research Laboratory, Pennsylvania StateUniversity (1975).

6. Freyer, G.J., Bremsstrahlung in the lower ionosphere,Scientific Report No. 336, Ionosphere ResearchLaboratory, Pennsylvania State University (1969).

7. Goldberg, R.A. and E.R. Hilsenrath, Operation Aurorozone:An experiment in Sun/Weather in third NASA weather andclimate program science review, ed. by E.R. Kreins,

* NASA CP 2029, 121, 1978.

8. Hale, L.C., Parameters of the low ionosphere at nightdeduced from parachute borne blunt probe measurements,Space Res. VII, 140, 1967.

9. Hale, L.C., D.P. Hoult and D.C. Baker, A summary ofblunt probe theory and experimental results, SpaceRes. VII, 320, 1968.

10. Mitchell, J.D., An experimental investigation ofmesospheric ionization, Scientific Report No. 416,Ionosphere Research Laboratory, Pennsylvania StateUniversity (1973)

11. Mitchell, J.D., R.S. Sagar and R.O. Olsen, Positive ionsin the middle atmosphere during sunrise conditions,Space Research XVII, 199, 1977.

.1

68

REFERENCES (cont'd)

12. Pedersen, A., Measurement of ion concentration in theD-region of the ionosphere with a Gerdien condenserrocket probe, FOA 3 Report A607, Research Instituteof National Defense, Stockhom, Sweden (1964).

13. Pomerantz, M.A. and S.P. Duggal, The sun and cosmicrays, Rev. Geophys. Space Phys., 12, 343, 1974.

14. Rose, G. and H.U. Widdel, Results of concentration andmobility measurements for positively and negativelycharged particles taken between 85 and 22 km in soundingrocket experiments, Radio Sci.77, 81, 1972.

15. Sagar, R.S., A subsonic Gerdien condenser experimentfor upper atmospheric research, Thesis Department ofElectrical Engineering, University of Texas at ElPaso (1976).

16. Velinov, P., On ionization in the ionospheric D-regionby galactic cosmic rays, J. Atmos. Terr. Phys. 30,1891, 1968.

17. Webber, W.R., The production of free electrons in theionospheric D layer by solar and galactic cosmic raysand the resultant absorption of radio waves, J. Geophys.Res. 67, 5091, 1962.

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